This invention provides an apparatus and method for preamble detection and integer carrier frequency offset estimation, which method comprises the steps of: determining the window of useful subcarriers in preamble transformed to frequency domain based on pre-determined possible integer carrier frequency offset and the length of the preamble, so as to select the useful subcarriers; extracting a plurality of subcarrier sequences having a length equal to that of the preamble from the useful subcarriers; calculating conjugative multiplications of each subcarrier and its neighboring subcarriers in the subcarrier sequences extracted; acquiring the real part of the conjugative multiplications; calculating the cross correlations between the real part of the conjugative multiplications and known preambles modulated by DBPSK, and outputting the calculated correlation values; and detecting preamble index of a target base station with the calculated correlation values to select a target cell, and estimating integer carrier frequency offset with respect to the target base station.